This invention relates to a method of depositing a thin film for a magnetic recording medium using a vacuum evaporation deposition method.
In recent years, the hard disk devices which are external storage devices in computers, image record/playback devices, and other equipment have a trend to have higher recording densities and smaller sizes. As a development in these devices, it has a demand for higher recording densities and smaller sizes for the purpose of the magnetic recording medium mounted in hard disk devices as well.
In order to enhance the recording density of a magnetic recording medium, the distance between the magnetic head and the magnetic layer of the magnetic recording medium (hereafter also called the magnetic spacing) must be reduced. In order to make the magnetic spacing smaller and lower the magnetic head flying height, the protective layer which is the uppermost surface formed on the magnetic layer of the magnetic recording medium must be thin. In addition, it is necessary that the film properties and step coverage of the protective layer be satisfactory.
In order to make the protective layer thinner, improvement in the durability and corrosion resistance of the thin film per unit film thickness is indispensable. Such a protective layer can, for example, be formed by using a sputtering method, CVD method, ion beam evaporation deposition method, or other methods.
Further, in a magnetic head, as described in Japanese Unexamined Patent Application Publication No. 2002-212713 (Patent Document 2), a formation of a tetrahedral amorphous carbon (ta-C) protective layer as a hard amorphous carbon film has been proposed. It has been proposed that such a protective layer can be formed by, for example, a FCVA (Filtered Cathodic Vacuum Arc) method (hereafter also called the FCVA method), as disclosed in Japanese Unexamined Patent Application Publication No. 2007-26506 (Patent Document 1), Patent Document 2, and National Publication of Translated Version No. 2007-501331 (Patent Document 3). It has been found that films obtained by the FCVA method have a low ratio of graphite components to diamond components, as well as excellent corrosion resistance and wear resistance.
However, while the FCVA method is maximally effective for attaining good film properties in the case of samples having extremely little surface roughness, step coverage is sometimes poor compared with the CVD method for magnetic recording media having relatively large relief patterns (pit series) on the surface. As a result, there are concerns that this method cannot be applied to discrete track media (DTM), which is regarded as a next-generation hard disk technology enabling high recording densities, or to magnetic recording media for patterned-media methods with relatively large surface relief patterns.
In the FCVA method, as means of enhancing the thin film adhesive strength, it has been proposed that the substrate on which the thin film is formed such that a direction of the substrate normal is inclined at a prescribed inclination angle α with respect to the direction of incidence of a plasma beam, and that the substrate is rotated, as described in Patent Document 2. When using this method, films deposited with this inclination angle α fixed at a constant angle in a range from 10° to 80° have poor step coverage as protective layers when the inclination angle is low, whereas when deposited at a high inclination angle, it is possible that damage to the magnetic layer already formed directly below the protective layer, such as the intrusion of carbon between crystal grains or destruction of crystals, cannot be avoided. That is, it is difficult to attain the improved step coverage and also reduce the damage to the magnetic layer.
Further, as another means of enhancing the thin film adhesive strength, it has been proposed that the incidence angle (inclination angle) relative to the substrate surface of the carbon plasma flow be fixed at each of a plurality of prescribed angles selected in a range from 15° to 45° during a carbon film formation to deposit the film, as described in Patent Document 3. However, when changing the inclination angle in stages without corresponding to the film thickness of the protective layer, it is difficult to achieve both improved step coverage and reduced damage to the magnetic layer.
In light of the above problems, this invention has as an object to obtain a method for depositing a thin film for a magnetic recording medium by using a vacuum evaporation deposition method and a film deposition apparatus using the same. The method for depositing a thin film for a magnetic recording medium is capable of depositing a thin film for a magnetic recording medium by the FCVA method having excellent step coverage, corrosion resistance, and wear resistance, even when deposited on a magnetic recording medium on the surface of which a comparatively large relief pattern is formed, as well as a film deposition apparatus using this method.
Further objects and advantages of the invention will be apparent from the following description of the invention.